Added trusted auth

Necessary because to actually use trusted auth, the core api does the following (https://github.com/woofound/core-api/blob/master/app/controllers/application_controller.rb)

      if trusted_auth? && user
        @current_user = user
        return
      end

      if user && user.valid_password?(password)
        @current_user = user
      else
        if !email.blank? || !password.blank?
          raise UserNotFound
        end
      end

Currently we require either an api token or both email and password.  We should be allowing password to be blank if we're using trusted auth